The invention relates to guidewires suitable for use in the deployment of implants for lung volume reduction.
In chronic obstructive pulmonary disease, damage to tissue in certain parts of the lungs means that normal muscular inflation and deflation of the lungs becomes less efficient. One method to improve this situation is lung volume reduction, in which the diseased tissue is compressed or collapsed so that the remaining tissue can behave more normally. In one form of lung volume reduction, one or more elongate spring implants are deployed into the airways in the diseased lung tissue and are allowed to contract, gathering up the diseased tissue as they do so. Implants and systems for such treatments are disclosed in WO 2007/106495 and WO 2010/030993. In both cases, implants are deployed into the airways from catheter systems. The airways of the lungs are highly branched and tortuous, and lung tissue can be easily damaged. Therefore guidewires are used to determine the path to the airway to be treated, the catheter for delivery of the implant being advanced over the guidewire, which is then removed so that the implant can be deployed through the properly positioned catheter.
The guidewire must be capable of being pushed out of the catheter and into airway, and rotated so that it advances in the desired direction, while at the same time being small enough that the delivery catheter can fit over it to be advanced into the lung for proper delivery of the implant. In order to reduce the likelihood of kinking due to the combination of compression and torsion, a composite structure has been proposed for the guidewire, comprising an inner core extending through an outer coil sheath. In order to allow the guidewire to be advanced through the catheter, the proximal part of the core is relatively thicker than the distal part, which is thinner to provide the necessary flexibility to be directed through the airways without damaging the lung tissue. One result of this is that applying torque at the proximal end of the guidewire to steer the distal end in the required direction can result in significant wind-up between the core and coil, making accurate control of the distal end difficult.
The invention attempt to address the problem of how to provide more accurate control of the distal end while retaining the necessary flexibility in the system.